1. Field of Invention
The present invention relates generally to a magnetic stirring apparatus.
2. Description of Related Art
The fields of biology and chemistry require the stirring of liquids and suspensions in target vials prior to and during sampling. Accordingly, a variety of stirring devices have been developed over the years, several of which were used in conjunction with autosamplers. Some previous devices utilized magnets mounted on motors that moved in space around or under the target vials. However, the motors only had an operating life of about 2000 hours, which made such designs unreliable for use with an autosampler that operates upwards of 8000 hours a year. Further, the placement of magnets between the target vials and the size of the magnets required to achieve active coupling with the stir bars decreased the number of vials that could be placed in a given area.
Other devices drove multiple stir bar locations simultaneously by placing pole shoes on top of coils and utilizing the pole shoes to direct a shared magnetic field under multiple vials placed in close proximity to one another. However, these pole shoe devices did not provide an acceptable consistent stirring action because the strength vector of the shared magnetic field became distorted by the magnetic stir bars placed in the vials. The distorted magnetic field resulted in the application of a strong magnetic field to the stir bars in some vials, and a weak magnetic field to the stir bars in other vials.
Accordingly, a need exists for a reliable stirring device that is capable of stirring samples contained in target vials placed in close proximity to one another and applies an individual and consistent magnetic field strength vector to the stir bar in each vial. The present invention addresses one or more of these needs.